EL display device

ABSTRACT

An EL display device capable of reducing an average film resistance of an anode in an EL device as well as displaying an image with high definition, and electrical equipment including such an EL display device are provided. A light-shielding metal film  109  is provided on an anode  108  so as to conceal gaps between the pixels. Thus, an average film resistance of the anode  108  in the EL device is reduced. Furthermore, light leakage from the gaps between the pixels can be prevented, resulting in an image display with high definition.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an EL (electro-luminescence)display device fabricated by forming a semiconductor device (a deviceutilizing a semiconductor thin film; typically a thin film transistor)onto a substrate. The present invention further relates to an electricalequipment including such an EL display device as a display section.

[0003] 2. Description of the Related Art

[0004] Recently, a technique for forming a thin film transistor(hereinafter referred to as TFT) onto a substrate has significantlyadvanced, and its application to an active-matrix display device hasbeen developed. In particular, the TFT employing a polysilicon filmtherein has a field effect mobility higher than that of the conventionalTFT employing an amorphous silicon film, and therefore, can operate athigher speed. Thus, a control function for pixels, that isconventionally performed by an external driver circuit provided at theoutside of the substrate, can be performed by a driver circuit that isprovided on the same substrate as the pixels.

[0005] The active-matrix display device as mentioned above can providevarious advantages such as reduction in the manufacturing cost,downsizing of the display device, improvement of the yield, reduction inthe throughput or the like, when various circuits and/or devices arefabricated on one and the same substrate. Thus, this kind ofactive-matrix display device has drawn much attention.

[0006] In an active-matrix EL display device, a switching deviceemploying a TFT (hereinafter referred to as switching TFT) is providedat each pixel, and each of the respective switching TFTs allows acorresponding drive device for controlling current (hereinafter referredto as current-controlling TFT) to drive, thereby causing an EL layer(more strictly speaking, a light emitting layer) to emit light. Anexemplary EL display device is described, for example, in JapanesePatent Application Laid-Open No. Hei. 10-189252.

[0007] The EL display device includes a device section composed of acathode, an EL layer, and an anode (hereinafter, the device composed ofthese portions is referred to as EL device). When a film resistance ofthe anode in the device section increases, the in-plane distribution ofelectrical potentials in the anode becomes non-uniform due to thevoltage drop, thereby resulting in disadvantages such as deviations inthe light intensity of the EL device.

SUMMARY OF THE INVENTION

[0008] Accordingly, an object of the present invention is to provide anEL display device having the structure capable of lowering a filmresistance of an anode in an EL device or exhibiting any correspondingadvantages. Furthermore, another objective of the present invention isto provide electrical equipment having a display section which operatesstably by employing such an EL display device as the display section.

[0009] The present invention will be described below with reference toFIG. 1. In FIG. 1, reference numeral 101 denotes a substrate having aninsulating surface. As the substrate 101, for example, an insulatingsubstrate such as a quartz substrate can be used. Alternatively, variouskinds of substrate, such as a glass substrate, a ceramic substrate, acrystallized glass substrate, a metal substrate, or a plastic substrate,can be used by providing an insulating film on a surface thereof.

[0010] On the substrate 101, pixels 102 are formed. Although only threeof the pixels are illustrated in FIG. 1, a higher number of pixels areactually arranged in matrix. Further, only one of the three pixels willbe described below, but the other pixels have the same configuration asthe explained one.

[0011] In each of the pixels 102, two TFTs are formed; one of them is aswitching TFT 103, and the other is a current-controlling TFT 104. Adrain of the switching TFT 103 is electrically connected to a gate ofthe current-controlling TFT 104. Furthermore, a drain of thecurrent-controlling TFT 104 is electrically connected to a pixelelectrode 105 (which, in this case, also functions as a cathode of an ELdevice). The pixel 102 is thus formed.

[0012] Various wirings of the TFT as well as the pixel electrode can beformed of a metal having a low resistivity. For example, an aluminumalloy may be used herein for this purpose.

[0013] Following the fabrication of the pixel electrode 105, aninsulating compound (referred to as alkaline compound hereinafter) 106containing an alkaline metal or an alkaline-earth metal is formed. Itshould be noted that the outline of the alkaline compound 106 isindicated by a dotted line in FIG. 1 because the compound 106 has athickness which is as thin as several nanometers, and it is not clearwhether the compound 106 is formed as a layer or in an island-shape.

[0014] As the above-mentioned alkaline compound 106, lithium fluoride(LiF), lithium oxide (Li₂O), barium fluoride (BaF₂), barium oxide (BaO),calcium fluoride (CaF₂), calcium oxide (CaO), strontium oxide (SrO), orcesium oxide (Cs₂O) can be used. Since these are insulating materials,electrical short-circuiting between the pixel electrodes does not occureven when the compound 106 is formed as a layer.

[0015] It is of course possible to use a known conductive material suchas a MgAg electrode as the cathode. However, in such a case, in order toavoid electrical short-circuiting between the pixel electrodes, thecathode itself has to be selectively formed or patterned into a certainshape.

[0016] Once the alkaline compound 106 is formed, an EL layer 107 (anelectro-luminescence layer) is formed over the compound 106. Any knownmaterial and/or structure can be employed for the EL layer 107. Morespecifically, with respect to the structure of the EL layer, only alight emitting layer for providing sites for the carrier recombinationmay be included in the EL layer. Alternatively, if necessary, anelectron injection layer, an electron transport layer, a hole transportlayer, an electron blocking layer, a hole device layer, or a holeinjection layer may be further layered to form the EL layer. In thepresent application, all of those layers intended to realize injection,transport or recombination of carriers are collectively referred to asthe EL layer.

[0017] As an organic material to be used as the EL layer 107, either alow-molecular type organic material or a polymer type (high-moleculartype) organic material can be used. However, it is desirable to use apolymer type organic material which can be formed by a film-formationmethod that can be easily performed, such as a spin coating method, aprinting method, or the like.

[0018] The structure illustrated in FIG. 1 is an example of themonochrome color light-emitting type in which an EL layer for emitting amonochrome color light, such as a red color, a blue color, a greencolor, a white color, a yellow color, an orange color, a purple color orthe like, is used for displaying a monotone image. The EL layer foremitting any monochrome color light as mentioned above may be formed ofknown materials.

[0019] Over the EL layer 107, a transparent conductive film is formed asan anode 108. As the transparent conductive film, a compound of indiumoxide and tin oxide (referred to as ITO), a compound of indium oxide andzinc oxide, tin oxide, or zinc oxide (ZnO) can be used.

[0020] In the present application, a film resistance of the whole anodeobtained by calculating an average of a film resistance for a regionwhere a metal film 109 and the anode 108 are layered and a filmresistance for only the anode (in other words, a film resistance of thewhole portion electrically connected to the anode) will be referred toas the average film resistance of the anode. By providing the metal film109 over the anode, the average film resistance in the anode can bedecreased. Furthermore, the metal film 109 also functions as a lightshielding film.

[0021] As a deposition technique for the metal film 109, a vapordeposition method is desirable in view of any possible damage to theanode during the deposition process.

[0022] In addition, upon the provision-of the metal film 109, it ispreferable to provide the metal film 109 so that gaps 111 between theadjacent pixel electrodes are concealed thereby when viewed from theviewing direction of a viewer (i.e., from the direction of the normal toa counter electrode). This is because of the fact that those gaps arenon-light emitting regions, as well as the fact that the electricalfield distribution becomes complicated in the vicinity of end portionsof the pixel electrodes so that light emission at a desired lightintensity or a desired chromaticity cannot be realized there.

[0023] After the metal film 109 is formed as mentioned above, aninsulating film as a second passivation film 112 is provided. As thepassivation film 112, a silicon nitride film or a silicon oxynitridefilm (represented as SiOxNy) is preferably used. Although it is possibleto use a silicon oxide film as the passivation film 112, it ispreferable to use an insulating film containing oxygen as little aspossible.

[0024] The substrate fabricated up to this stage is referred to as anactive-matrix substrate in the present application. More specifically,the substrate on which TFTs, pixel electrodes respectively electricallyconnected to the TFTs, as well as EL devices each composed of an ELlayer, an anode, and a metal film and utilizing the corresponding pixelelectrode as a cathode are formed is referred to as the active-matrixsubstrate.

[0025] Furthermore, a counter substrate 110 is attached to theactive-matrix substrate so that the EL devices are interposed and sealedtherebetween. Although not illustrated herein, the counter substrate 110is adhered to the active-matrix substrate by means of a sealing agent,so that a space designated with reference numeral 113 becomes a closedspace.

[0026] As the counter substrate 110, it is necessary to use atransparent substrate so as not to prevent light from passingtherethrough. For example, a glass substrate, a quartz substrate, or aplastic substrate is preferably used.

[0027] The closed space 113 may be filled with inert gas (noble gas ornitrogen gas), or with inert liquid. Alternatively, the closed space 113may be filled with a transparent additive agent or resin so as to adherethe whole surface of the substrate. Moreover, it is preferable todispose a drying agent such as barium oxide or the like in the closedspace 113. Since the EL layer 107 is very vulnerable to water, it isdesirable to prevent water from entering the closed space 113 as much aspossible.

[0028] In the EL display device having the above-described configurationin accordance with the present invention, light emitted from the ELdevice passes through the counter substrate to be emitted to reach theviewer's eyes. Accordingly, the viewer can recognize an image throughthe counter substrate side. In this situation, one of the features ofthe EL display device in accordance with the present invention is thatthe metal film 109 having a low electrical resistivity is disposed onthe anode 108 included in the EL device so that the gaps 111 between theadjacent pixel electrodes 105 are concealed by the metal film 109. Thisresults in a decreased average film resistance of the anode in the ELdevice as well as prevention of light leakage from the gaps 111 betweenthe pixel electrodes 105. Thus, an image can be displayed with clearcontours between the pixels.

[0029] Thus, in accordance with implementing the present invention, anEL display device capable of having a reduced average film resistance ofan anode in the EL device section as well as displaying an image withclear contours between the pixel electrodes can be provided.Furthermore, electrical equipment employing such an EL display device asa display section can be also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 is a view for illustrating a pixel section of an EL displaydevice.

[0031]FIG. 2 is a view for illustrating a cross-sectional structure of apixel of the EL display device.

[0032]FIGS. 3A and 3B are a view for illustrating a top structure of thepixel section of the EL display device and a view for illustrating theconfiguration of the pixel section of the EL display device,respectively.

[0033]FIGS. 4A through 4E are views for respectively illustrating thefabricating steps of an active-matrix EL display device.

[0034]FIGS. 5A through 5D are views for respectively illustrating thefabricating steps of the active-matrix EL display device.

[0035]FIGS. 6A through 6C are views for respectively illustrating thefabricating steps of the active-matrix EL display device.

[0036]FIG. 7 is a perspective view for illustrating an externalappearance of an EL module.

[0037]FIG. 8 is a view for illustrating the circuit configuration of theEL display device.

[0038]FIG. 9 is an expanded view of the pixel in the EL display device.

[0039]FIG. 10 is a view for illustrating the structure of a samplingcircuit of the EL display device.

[0040]FIGS. 11A and 11B are a perspective view for illustrating anexternal appearance of the EL module and a view for illustrating across-sectional structure of the EL module, respectively.

[0041]FIG. 12 is a view for illustrating the configuration of a pixel ofthe EL display device.

[0042]FIGS. 13A through 13F are views for respectively illustratingspecific examples of electrical equipment.

[0043]FIGS. 14A and 14B are views for respectively illustrating specificexamples of electrical equipment.

[0044]FIG. 15 is a view for illustrating a pixel section of the ELdisplay device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] One of various embodiments of the present invention will bedescribed with reference to FIGS. 2, 3A, and 3B. FIG. 2 shows across-sectional view of a pixel section of the EL display device inaccordance with the present invention. FIG. 3A shows a top view of thepixel section and FIG. 3B shows the circuit configuration therefor. Thepixel section (image display section) is actually configured byarranging a plurality of pixels in matrix. FIG. 2 corresponds to across-sectional view obtainable by cutting FIG. 3A along line A-A′.Accordingly, the same reference numerals are commonly used among FIGS.2, 3A, and 3B for convenience when viewing those drawings. Furthermore,two pixels illustrated in the top view of FIG. 3A have the identicalstructure with each other.

[0046] In FIG. 2, a reference numeral 11 designates a substrate; and 12,an insulating film (hereinafter referred to as base film) which becomesan undercoat. A glass substrate, a glass ceramic substrate, a quartzsubstrate, a silicon substrate, a ceramic substrate, a metal substrate.or a plastic substrate (including a plastic film as well) can be used asthe substrate 11.

[0047] A base film 12 is particularly effective in the case where asubstrate containing movable ions or a conductive substrate is used asthe substrate 11. It is not necessary to provide the base film 12 when aquartz substrate is used as the substrate 11. As the base film 12, aninsulating film containing silicon can be used. In the presentapplication, the term “insulating film containing silicon” refers to aninsulating film containing silicon, oxygen or nitrogen at apredetermined ratio, specifically, a silicon oxide film, a siliconnitride film, or a silicon oxynitride film (represented as SiOxNy.)

[0048] Here, two TFTs are formed in the pixel. A reference numeral 201designates a TFT (hereinafter referred to as switching TFT) functioningas a switching element; and 202, a TFT (hereinafter referred to ascurrent controlling TFT) functioning as a current controlling elementfor controlling the amount of current flowing to the EL element. Bothare formed out of an n-channel TFT.

[0049] An n-channel type TFT has a field effect mobility larger thanthat of a p-channel type TFT, and therefore, can be operated at higherspeed and allow a larger amount of current to flow, as compared to thep-channel type TFT. The smaller-sized n-channel type TFT can allow thesame amount of current to flow therethrough as the p-channel type TFT.Accordingly, it is preferable to employ the n-channel type TFT as thecurrent-controlling TFT because larger effective area of the displaysection can be obtained.

[0050] In the p-channel type TFT, hot carrier injection is almostnegligible. In addition, an OFF current value of the p-channel type TFTis low. Due to these advantages, the p-channel type TFT has been used insome reports as the switching TFT or the current-controlling TFT.However, in accordance with the present invention, disadvantagesconcerning the hot carrier injection and the OFF current value areovercome even for the n-channel type TFT by providing LDD regions atshifted positions. This leads to another feature of the presentinvention in that all of the TFTs to be used in every pixel aren-channel type TFTs.

[0051] It should be noted, however, that in the present invention, theswitching TFT and the current-controlling TFT are not limited to be then-channel type TFT. Alternatively, a p-channel type TFT can be usedeither as the switching TFT or as the current-controlling TFT, or asboth of them.

[0052] The switching TFT 201 is formed having: an active layercontaining a source region 13, a drain region 14, LDD regions 15 a to 15d, a high concentration impurity region 16, and channel forming regions17 a and 17 b; a gate insulating film 18; gate electrodes 19 a and 19 b;a first interlayer insulating film 20; a source wiring 21; and a drainwiring 22.

[0053] In addition, as illustrated in FIGS. 3A and 3B, gate electrodes19 a and 19 b are electrically connected with each other by means of agate wiring 211 made of a different material having a lower electricalresistance, thereby resulting in the double-gate structure. It should benoted that not only the double-gate structure, but also any othermulti-gate structure such as the triple-gate structure, (i.e., astructure including an active layer that has two or more channel-formingregions connected in series to each other) can be used. The multi-gatestructure is very effective for realizing reduction in an OFF currentvalue. In the present invention, a switching device with a low OFFcurrent value can be realized by providing the switching device 201 inthe pixel with the multi-gate structure.

[0054] The active layer is formed out of a semiconductor film containinga crystal structure. That is, a single crystal semiconductor film may beused or a polycrystalline semiconductor film or microcrystallinesemiconductor film may be used. The gate insulating film 18 may beformed out of an insulating film containing silicon. Besides, anyconductive films can be used for the gate electrodes, source wiringline, or drain wiring line.

[0055] Furthermore, in the switching TFT 201, LDD regions 15 a to 15 dare provided at such positions so as not to overlap the gate electrodes19 a and 19 b with a gate insulating film 18 interposed therebetween.This kind of structure is highly effective for reducing an OFF currentvalue.

[0056] In the case where the multi-gate structure with two or more gateelectrodes being employed is provided, a high-concentration impurityregion disposed between the channel-forming regions is effective forreducing an OFF current value.

[0057] As described above, by using the TFT of the multi-gate structureas the switching element 201 of the pixel, it is possible to realize theswitching element having a sufficiently low off current value. Thus,even if a condenser as shown in FIG. 2 of Japanese Patent ApplicationLaid-open No. Hei 10-189252 is not provided, the gate voltage of thecurrent controlling TFT can be held for a sufficient time (an intervalbetween a selected point and a next selected point).

[0058] Next, the current controlling TFT 202 is formed by including asource region 31, a drain region 32, an active layer including an LDDregion 33 and a channel forming region 34, a gate insulating film 18, agate electrode 35, the first interlayer insulating film 20, a sourcewiring line 36, and a drain wiring line 37. Although the gate electrode35 is of a single gate structure, a multi-gate structure may be adopted.

[0059] As shown in FIG. 2, the drain of the switching TFT 201 isconnected to the gate of the current controlling TFT 202. Specifically,the gate electrode 35 of the current controlling TFT 202 is electricallyconnected to the drain region 14 of the switching TFT 201 through thedrain wiring line (may be called a connection wiring line) 22. Thesource wiring line 36 is connected to a current supply line 212 (FIG.3A).

[0060] Although the current controlling TFT 202 is an element forcontrolling the amount of current injected to an EL element 203, in viewof deterioration of the EL element, it is not desirable to supply alarge amount of current. Thus, in order to prevent excessive currentfrom flowing to the current controlling TFT 202, it is preferable todesign the channel length (L) to be rather long. Desirably, it isdesigned so that the current becomes 0.5 to 2 μm (preferably 1 to 1.5μm) per pixel.

[0061] In view of the above, as shown in FIG. 9, when the channel lengthof the switching TFT is L1 (L1=L1a+L1b), the channel width is W1, thechannel length of the current controlling TFT is L2, and the channelwidth is W2, it is preferable that W1 is made 0.1 to 5 μm (typically 0.5to 2 μm), and W2 is made 0.5 to 10 μm (typically 2 to 5 μm). Besides, itis preferable that L1 is made 0.2 to 18 μm (typically 2 to 15 μm), andL2 is made 1 to 50 μm (typically 10 to 30 μm). However, the presentinvention is not limited to the above numerical values.

[0062] Besides, it is appropriate that the length (width) of the LDDregion formed in the switching TFT 201 is made 0.5 to 3.5 μm, typically2.0 to 2.5 μm.

[0063] In the EL display device as illustrated in FIG. 2, an LDD region33 is provided between a drain region 32 and a channel-forming region 34in the current-controlling TFT 202. Although in the illustratedstructure, the LDD region 33 includes a region overlapping a gateelectrode with a gate insulating film 18 interposed therebetween as wellas a region that does not overlap the gate electrode 35, it is possibleto form another structure in which the LDD region 33 is configured onlywith a region overlapping the gate electrode 35 with the gate insulatingfilm 18 interposed therebetween.

[0064] The current controlling TFT 202 supplies current to cause the ELelement 203 to emit light, and at the same time controls the supplyamount to enable gradation display. Thus, it is necessary to take acountermeasure against deterioration due to the hot carrier injection sothat deterioration does not occur even if current is supplied.

[0065] With respect to deterioration due to the hot carrier injection,it is known that the LDD region overlapping the gate electrode issignificantly effective. Accordingly, the structure in which the LDDregion is provided in regions overlapping the gate electrode 35 with thegate insulating film 18 interposed therebetween is suitable forsuppressing the hot carrier injection. However, in the illustratedstructure of the present embodiment, another LDD region that does notoverlap the gate electrode is also provided as the countermeasure forthe disadvantages relating to the OFF current. It should be noted,however, that the LDD region not overlapping the gate electrode is notnecessarily required to be provided.

[0066] In addition, when the overlapping length of the LDD region underthe gate electrode is too long, an ON current gets reduced, while thehot carrier prevention effect becomes weakened when the overlappinglength is too short.

[0067] Thus, in the present embodiment, the LDD region that overlaps thegate electrode is provided at the overlapping length determined in viewof the above-mentioned facts, as illustrated in FIG. 2. Furthermore, thecapacitance created by providing the LDD region overlapping the gateelectrode is employed as a storage capacitance.

[0068] In the above structure, parasitic capacity is formed in theregion where the gate electrode and the LDD region overlap with eachother. Thus, it is preferable not to provide such region betweenthe-source region 31 and the channel forming region 34. In the currentcontrolling TFT, since the direction of flow of carriers (here,electrons) is always the same, it is sufficient if the LDD region isprovided at only the side of the drain region.

[0069] From the view point of increasing an amount of current that canflow, it is also effective to provide an active layer (in particular, achannel-forming region thereof) in the current-controlling TFT 202 tohave a large film thickness (preferably in the range from 50 to 100 nm,and more preferably in the range from 60 to 80 nm). Conversely, withrespect to the switching TFT 201, it is also effective to provide anactive layer (in particular, a channel-forming region thereof) in theswitching TFT 201 to have a small film thickness (preferably in therange from 20 to 50 nm, and more preferably in the range from 25 to 40nm) in order to suppress an OFF current value.

[0070] Then, reference numeral 41 denotes a first passivation film. Afilm thickness of the first passivation film 41 may be set in the rangefrom 10 nm to 1 μm (preferably, 200 to 500 nm). As the material of thepassivation film 41, an insulating film containing silicon can be used(in particular, a silicon oxynitride film or a silicon nitride film ispreferable).

[0071] Over the first passivation film 41, a second interlayerinsulating film 42 (also referred to as planarizing film) is formed tocover the respective TFTs, so that steps introduced by the TFTs areplanarized. As the second interlayer insulating film 42, an organicresin film is preferably used. For example, a polyimide film, apolyamide film, an acrylic film, a BCB (benzocyclobutene) film or thelike may be used. It is of course possible to use an inorganic film solong as sufficient planarization can be realized.

[0072] The planarization of the steps, caused by TFTs, with the secondinterlayer insulating film 42 is very important. Since the EL layer tobe formed later is very thin, any underlying steps may lead toinsufficient light emission. Accordingly, it is preferable to performthe planarization process prior to the formation of pixel electrodes soas to form the EL layer on a surface as flat as possible.

[0073] Reference numeral 43 denotes a pixel electrode (corresponding toa cathode of the EL device) made of a conductive film having lightshielding properties. After forming a contact hole (an opening hole)through the second interlayer insulating film 42 and a first passivationfilm 41, the pixel electrode 43 is formed to be connected to a drainwiring 37 of the current-controlling TFT 202 at the formed opening holesection.

[0074] On the pixel electrode 43, a lithium fluoride film having athickness in the range from 5 to 10 nm is formed as an alkaline compound44 by a vapor deposition method. The lithium fluoride film is aninsulating film, and therefore, a current cannot flow toward the ELlayer when a film thickness of the lithium fluoride film is too thick.No adverse problem will be introduced even when the lithium fluoridefilm is formed, not in a layer, but in an island-shape.

[0075] The EL layer 45 is then formed. In the present embodiment, apolymer-type organic material is formed by a spin coating method. As thepolymer-type organic material, any known material can be used. Inaddition, in the present embodiment, a single layer which is a lightemitting layer is used as the EL layer 45. Alternatively, when the ELlayer has a layered structure in which the light emitting layer iscombined with a hole transport layer and/or an electron transport layer,a higher light emission efficiency can be obtained. It should be notedthat when a polymer-type organic material is layered, it is preferableto combine it with a low-molecular organic compound formed by a vapordeposition method. The reason therefor is as follows. In a spin coatingmethod, an organic material to form the EL layer is mixed into anorganic solvent and then applied onto an underlying surface.Accordingly, any organic material, if existing in the underlying layer,may dissolve again in the applied organic solvent.

[0076] Typical polymer-type organic materials that can be used in thepresent embodiment include various high-molecular materials such as apolyparaphenylenevinylene (PPV) type material, a polyvinylcarbazole(PVK) type material, a polyfluorene type material, or the like. When anelectron transport layer, a light emitting layer, a hole transportlayer, or a hole injection layer is to be formed of the above-mentionedpolymer-type organic materials, these materials may be applied in thecondition of a polymer precursor and then heated (baked) in vacuum to betransferred into an intended polymer type organic materials.

[0077] More specifically, for forming a light emitting layer,cyanopolyphenylenevinylene may be used for a red-color light emittinglayer, polyphenylenevinylene may be used for a green-color lightemitting layer, and polyphenylenevinylene or polyalkylphenylene may beused for a blue-color light emitting layer. A film thickness of theabove layers may be set in the range from 30 to 150 nm (preferably inthe range from 40 to 100 nm). In addition, for forming a hole transportlayer, polytetrahydrothiophenylphenylene which is a polymer precursor isused, which is then transferred into polyphenylenevinylene by a heatingtreatment. A film thickness of the above layer may be set in the rangefrom 30 to 100 nm (preferably in the range from 40 to 80 nm.)

[0078] It is also possible to realize white-color light emission with apolymer-type organic material. For that purpose, techniques described inJapanese Patent Application Laid-Open Nos. Hei. 8-96959, 7-220871,9-63770, or the like maybe employed. Since the polymer-type organicmaterial can easily realize color adjustment by adding a fluorescentpigment into a solution in which a host material is being dissolved, thematerial is particularly effective for obtaining the white-color lightemission.

[0079] It should be noted that the above-mentioned materials are merelyexamples that can be used as an EL layer in the present invention. It isnot intended to limit the present invention to those materials.

[0080] In addition, although it is described in the above to use apolymer-type organic material for forming an EL device, a low-moleculartype organic material can be used for that purpose. Furthermore, the ELlayer can be made of an inorganic material.

[0081] Upon the formation of the EL layer 45, it is desirable to performthe formation process in a dry inert gas atmosphere which contains waterof as less amount as possible. Since the EL layer easily deterioratesdue to existence of water or oxygen, these factors should be eliminatedas perfectly as possible upon the formation of the EL layer. Forexample, a dry nitrogen atmosphere, a dry argon atmosphere or the likeis preferable. Accordingly, it is desirable to accommodate a chamber tobe used for an application process or a chamber to be used for a bakingprocess, in a clean booth filled with inert gas, and perform the processin such an atmosphere.

[0082] Following the formation of the EL layer 45 as described above, ananode 46 made of a transparent conductive film is then formed. In thepresent embodiment, a conductive film made of a compound of indium oxideand tin oxide is used as the anode 46. A small amount of gallium may beadded thereto.

[0083] Then, a light-shielding metal film 47 (47 a, 47 b) is formed onthe anode 46. In the present embodiment, the metal film 47 is disposedso as to conceal the gap between the pixel electrode 43 and the adjacentpixel electrode, and is intended to function as a light shielding film.In the present embodiment, a film resistance of the metal film 47 is setto be lower than the film resistance (also referred to as the sheetresistance) of the anode 46.

[0084] Close adhesion of the metal film 47 to the anode material is alsoimportant. Although it is important to use a proper metal material inorder to obtain enhanced close adhesion, it is also effective tooptimize conditions for the film deposition of the anode (a conductivefilm made of a compound of indium oxide and tin oxide in the presentembodiment) and conditions for a heat treatment to be performed afterthe film deposition.

[0085] As the metal film 47, it is desirable to use a metal materialhaving a low resistivity (also referred to as specific resistance). Forexample, titanium (Ti), aluminum (Al), tantalum (Ta), tungsten (W),chromium (Cr), copper (Cu), silver (Ag) or the like can be used as themetal material having a low resistivity.

[0086] Moreover, in the present embodiment, the metal film 47, which isto be formed directly on the anode 46, is desirably formed by a vapordeposition method. A film thickness thereof may be set in the range from30 to 100 nm (preferably in the range from 40 to 80 nm.) Following theformation of the metal film 47 as described above, a second passivationfilm 48 is formed. In the present embodiment, a silicon nitride filmhaving a thickness in the range from 10 nm to 1 μm (preferably in therange from 200 to 500 nm) is used as the second passivation film 48.

[0087] A counter substrate 49 is provided so as to face the thuscompleted active-matrix substrate. In the present embodiment, a glasssubstrate is used as the counter substrate 49.

[0088] The active-matrix substrate and the counter substrate 49 areadhered to each other by means of a sealing agent (not illustrated) toform a closed space 50. In the present embodiment, the closed space 50is filled with argon gas. It is also possible to dispose a drying agentas mentioned previously in the closed space 50.

[0089] The EL display device in the present embodiment has a pixelsection composed of the pixel that has the structure as illustrated inFIG. 2. Furthermore, the two types of TFTs having different structuresbased on their functions are disposed in the pixel. More specifically,the switching TFT, that has a sufficiently low OFF current value, andthe current-controlling TFT, that is capable of withstanding against theinjection of hot carriers, are formed in the same pixel, therebyresulting in an EL display device that has a high reliability and iscapable of reducing a resistance of an EL device therein.

[0090] [Embodiment 1]

[0091] The embodiments of the present invention are explained usingFIGS. 4A to 6C. A method of simultaneous manufacturing of a pixelportion, and TFTs of a driver circuit portion formed in the periphery ofthe pixel portion, is explained here. Note that in order to simplify theexplanation, a CMOS circuit is shown as a basic circuit for the drivercircuits.

[0092] First, as shown in FIG. 4A, a base film 301 is formed with a 300nm thickness on a glass substrate 300. Silicon oxynitride films arelaminated as the base film 301 in embodiment 1. It is good to set thenitrogen concentration at between 10 and 25 wt % in the film contactingthe glass substrate 300.

[0093] Besides, as a part of the base film 301, it is effective toprovide an insulating film made of a material similar to the firstpassivation film 41 shown in FIG. 2. The current controlling TFT is aptto generate heat since a large current is made to flow, and it iseffective to provide an insulating film having a heat radiating effectat a place as close as possible.

[0094] Next, an amorphous silicon film (not shown in the figures) isformed with a thickness of 50 nm on the base film 301 by a knowndeposition method. Note that it is not necessary to limit this to theamorphous silicon film, and another film may be formed provided that itis a semiconductor film containing an amorphous structure (including amicrocrystalline semiconductor film). In addition, a compoundsemiconductor film containing an amorphous structure, such as anamorphous silicon-germanium film, may also be used. Further, the filmthickness may be made from 20 to 100 nm.

[0095] The amorphous silicon film is then crystallized by a knownmethod, forming a crystalline silicon film (also referred to as apolycrystalline silicon film or a polysilicon film) 302. Thermalcrystallization using an electric furnace, laser annealingcrystallization using a laser, and lamp annealing crystallization usingan infrared lamp exist as known crystallization methods. Crystallizationis performed in this embodiment using an excimer laser light which usesXeCl gas.

[0096] Note that pulse emission type excimer laser light formed into alinear shape is used in this embodiment, but a rectangular shape mayalso be used, and continuous emission argon laser light and continuousemission excimer laser light can also be used.

[0097] In this embodiment, although the crystalline silicon film is usedas the active layer of the TFT, it is also possible to use an amorphoussilicon film. Further, it is possible to form the active layer of theswitching TFT, in which there is a necessity to reduce the off current,by the amorphous silicon film, and to form the active layer of thecurrent control TFT by the crystalline silicon film. Electric currentflows with difficulty in the amorphous silicon film because the carriermobility is low, and the off current does not easily flow. In otherwords, the most can be made of the advantages of both the amorphoussilicon film, through which current does not flow easily, and thecrystalline silicon film, through which current easily flows.

[0098] Next, as shown in FIG. 4B, a protective film 303 is formed on thecrystalline silicon film 302 with a silicon oxide film having athickness of 130 nm. This thickness may be chosen within the range of100 to 200 nm (preferably between 130 and 170 nm). Furthermore, otherfilms may also be used providing that they are insulating filmscontaining silicon. The protective film 303 is formed so that thecrystalline silicon film is not directly exposed to plasma duringaddition of an impurity, and so that it is possible to have delicateconcentration control of the impurity.

[0099] Resist masks 304 a and 304 b are then formed on the protectivefilm 303, and an impurity element which imparts n-type conductivity(hereafter referred to as an n-type impurity element) is added via theprotective film 303. Note that elements residing in periodic table group15 are generally used as the n-type impurity element, and typicallyphosphorous or arsenic can be used. Note that a plasma doping method isused, in which phosphine (PH₃) is plasma activated without separation ofmass, and phosphorous is added at a concentration of 1×10⁸ atoms/cm³ inthis embodiment. An ion implantation method, in which separation of massis performed, may also be used, of course.

[0100] The dose amount is regulated so that the n-type impurity elementis contained in n-type impurity regions 305 and 306, thus formed by thisprocess, at a concentration of 2×10¹⁶ to 5×10¹⁹ atoms/cm³ (typicallybetween 5×10¹⁷ and 5×10¹⁸ atoms/cm³).

[0101] Next, as shown in FIG. 4C, the protective film 303, resist masks304 a and 304 b are removed, and an activation of the added periodictable group 15 elements is performed. A known technique of activationmay be used as the means of activation, but activation is done in thisembodiment by irradiation of excimer laser light. Of course, a pulseemission type excimer laser and a continuous emission type excimer lasermay both, be used, and it is not necessary to place any limits on theuse of excimer laser light. The goal is the activation of the addedimpurity element, and it is preferable that irradiation is performed atan energy level at which the crystalline silicon film does not melt.Note that the laser irradiation may also be performed with theprotective film 303 in place.

[0102] The activation by heat treatment may also be performed along withactivation of the impurity element by laser light. When activation isperformed by heat treatment, considering the heat resistance of thesubstrate, it is good to perform heat treatment on the order of 450 to550° C.

[0103] A boundary portion (connecting portion) with end portions of then-type impurity regions 305 and 306, namely regions, in which the n-typeimpurity element is not added, on the periphery of the n-type impurityregions 305 and 306, is not added, is delineated by this process. Thismeans that, at the point when the TFTs are later completed, extremelygood connections can be formed between LDD regions and channel formingregions.

[0104] Unnecessary portions of the crystalline silicon film are removednext, as shown in FIG. 4D, and island shape semiconductor films(hereafter referred to as active layers) 307 to 310 are formed.

[0105] Then, as shown in FIG. 4E, a gate insulating film 311 is formed,covering the active layers 307 to 310. An insulating film containingsilicon and with a thickness of 10 to 200 nm. preferably between 50 and150 nm, may be used as the gate insulating film 311. A single layerstructure or a lamination structure may be used. A 110 nm thick siliconoxynitride film is used in this embodiment.

[0106] Thereafter, a conductive film having a thickness of 200 to 400 nmis formed and patterned to form gate electrodes 312 to 316. Respectiveend portions of these gate electrodes 312 to 316 may be tapered. In thepresent embodiment, the gate electrodes and wirings (hereinafterreferred to as the gate wirings) electrically connected to the gateelectrodes for providing lead wires are formed of different materialsfrom each other. More specifically the gate wirings are made of amaterial having a lower resistivity than the gate electrodes. Thus, amaterial enabling fine processing is used for the gate electrodes, whilethe gate wirings are formed of a material that can provide a smallerwiring resistance but is not suitable for fine processing. It is ofcourse possible to form the gate electrodes and the gate wirings withthe same material.

[0107] Although the gate electrode can be made of a single-layeredconductive film, it is preferable to form a lamination film with two,three or more layers for the gate electrode if necessary. Any knownconductive materials can be used for the gate electrode. It should benoted, however, that it is preferable to use such a material thatenables fine processing, and more specifically, a material that can bepatterned with a line width of 2 μm or less.

[0108] Typically, it is possible to use a film made of an elementselected from tantalum (Ta). titanium (Ti), molybdenum (Mo), tungsten(W), chromium (Cr), and silicon (Si), a film of nitride of the aboveelement (typically a tantalum nitride film, tungsten nitride film, ortitanium nitride film), an alloy film of combination of the aboveelements (typically Mo—W alloy, Mo—Ta alloy), or a silicide film of theabove element (typically a tungsten silicide film or titanium silicidefilm). Of course, the films may be used as a single layer or a laminatelayer.

[0109] In this embodiment, a laminate film of a tungsten nitride (WN)film having a thickness of 50 nm and a tungsten (W) film having athickness of 350 nm is used. This may be formed by a sputtering method.When an inert gas of Xe, Ne or the like is added as a sputtering gas,film peeling due to stress can be prevented.

[0110] The gate electrodes 313 and 316 are formed at this time so as tooverlap a portion of the n-type impurity regions 305 and 306,respectively, sandwiching the gate insulating film 311. This overlappingportion later becomes an LDD region overlapping the gate electrode.

[0111] Next, an n-type impurity element (phosphorous in this embodiment)is added in a self-aligning manner with the gate electrodes 312 to 316as masks, as shown in FIG. 5A. The addition is regulated so thatphosphorous is added to impurity regions 317 to 323 thus formed at aconcentration of {fraction (1/10)} to ½ that of the impurity regions 305and 306 (typically between ¼ and ⅓). Specifically, a concentration of1×10¹⁶ to 5×10¹⁸ atoms/cm³ (typically 3×10¹⁷ to 3×10¹⁸ atoms/cm³) ispreferable.

[0112] Resist masks 324 a to 324 d are formed next, with a shapecovering the gate electrodes etc., as shown in FIG. 5B, and an n-typeimpurity element (phosphorous is used in this embodiment) is added,forming impurity regions 325 to 331 containing high concentration ofphosphorous. Ion doping using phosphine (PH₃) is also performed here,and is regulated so that the phosphorous concentration of these regionsis from 1×10²⁰ to 1×10²¹ atoms/cm³ (typically between 2×10²⁰ and 5×10²⁰atoms/cm³).

[0113] A source region or a drain region of the n-channel type TFT isformed by this process, and in the switching TFT, a portion of then-type impurity regions 320 to 322 formed by the process of FIG. 5A areremained. These remaining regions correspond to the LDD regions 15 a to15 d of the switching TFT in FIG. 2.

[0114] Next, as shown in FIG. 5C, the resist masks 324 a to 324 d areremoved, and a new resist mask 332 is formed. A p-type impurity element(boron is used in this embodiment) is then added, forming impurityregions 333 and 334 containing boron at high concentration. Boron isadded here to form impurity regions 333 and 334 at a concentration of3×10²⁰ to 3×10²¹ atoms/cm³(typically between 5×10²⁰ and 1×10²¹atoms/cm³) by ion doping using diborane (B₂H₆).

[0115] Note that phosphorous has already been added to the impurityregions 333 and 334 at a concentration of 1×10²⁰ to 1×10²¹ atoms/cm³,but boron is added here at a concentration of at least three times morethan that of the phosphorous. Therefore, the n-type impurity regionsalready formed completely invert to p-type, and function as p-typeimpurity regions.

[0116] Next, after removing the resist mask 332, the n-type and p-typeimpurity elements added to the active layer at respective concentrationsare activated. Furnace annealing, laser annealing or lamp annealing canbe used as a means of activation. In this embodiment, heat treatment isperformed for 4 hours at 550° C. in a nitrogen atmosphere in an electricfurnace.

[0117] At this time, it is critical to eliminate oxygen from thesurrounding atmosphere as much as possible. This is because when evenonly a small amount of oxygen exists, an exposed surface of the gateelectrode is oxidized, which results in an increased resistance andlater makes it difficult to form an ohmic contact with the gateelectrode. Accordingly, the oxygen concentration in the surroundingatmosphere for the activation process is set at 1 ppm or less,preferably at 0.1 ppm or less.

[0118] After the activation process is completed, the gate wiring 335having a thickness of 300 nm is formed as shown in FIG. 5D. As amaterial for the gate wiring 335, a metal film containing aluminum (Al)or copper (Cu) as its main component (occupied 50 to 100% in thecomposition) can be used. The gate wiring 335 is arranged, as the gatewiring 211 shown in FIG. 3, so as to provide electrical connection forthe gate electrodes 19 a and 19 b (corresponding to the gate electrodes314 and 315 in FIG. 4E) of the switching TFT.

[0119] The above-described structure can allow the wiring resistance ofthe gate wiring to be to significantly reduced, and therefore, an imagedisplay region (pixel portion) with a large area can be formed. Morespecifically, the pixel structure in accordance with the presentembodiment is advantageous for realizing an EL display device having adisplay screen with a diagonal size of 10 inches or larger (or 30 inchesor larger.)

[0120] A first interlayer insulating film 336 is formed next, as shownin FIG. 6A. A single layer insulating film containing silicon is used asthe first interlayer insulating film 336, while a lamination film, whichis a combination of insulating film including two or more kinds ofsilicon, may be used. Further, a film thickness of between 400 nm and1.5 μm may be used. A lamination structure of an 800 nm thick siliconoxide film on a 200 nm thick silicon oxynitride film is used in thisembodiment.

[0121] In addition, heat treatment is performed for 1 to 12 hours at 300to 450° C. in an atmosphere containing between 3 and 100% hydrogen,performing hydrogenation. This process is one of hydrogen termination ofdangling bonds in the semiconductor film by hydrogen which is thermallyactivated. Plasma hydrogenation (using hydrogen activated by a plasma)may also be performed as another means of hydrogenation.

[0122] Note that the hydrogenation processing may also be insertedduring the formation of the first interlayer insulating film 336.Namely, hydrogen processing may be performed as above after forming the200 nm thick silicon oxynitride film, and then the remaining 800 nmthick silicon oxide film may be formed.

[0123] Next, a contact hole is formed in the first interlayer insulatingfilm 336 and the gate insulating film 311, and source wiring lines 337to 340 and drain wiring lines 341 to 343 are formed. In this embodiment,this electrode is made of a laminate film of three-layer structure inwhich a titanium film having a thickness of 100 nm, an aluminum filmcontaining titanium and having a thickness of 300 nm, and a titaniumfilm having a thickness of 150 nm are continuously formed by asputtering method. Of course, other conductive films may be used.

[0124] A first passivation film 344 is formed next with a thickness of50 to 500 nm (typically between 200 and 300 nm). A 300 nm thick siliconoxynitride film is used as the first passivation film 344 in thisembodiment. This may also be substituted by a silicon nitride film. Itis of course possible to use the same materials as those of the firstpassivation film 41 of FIG. 2.

[0125] Note that it is effective to perform plasma processing using agas containing hydrogen such as H₂ or NH₃ etc. before the formation ofthe silicon oxynitride film. Hydrogen activated by this preprocess issupplied to the first interlayer insulating film 336, and the filmquality of the first passivation film 344 is improved by performing heattreatment. At the same time, the hydrogen added to the first interlayerinsulating film 336 diffuses to the lower side, and the active layerscan be hydrogenated effectively.

[0126] Next, as shown in FIG. 6B, a second interlayer insulating film345 made of organic resin is formed. As the organic resin, it ispossible to use polyimide, polyamide, acryl, BCB (benzocyclobutene) orthe like. Especially, since the second interlayer insulating film 345 isprimarily used for flattening, acryl excellent in flattening propertiesis preferable. In this embodiment, an acrylic film is formed to athickness sufficient to flatten a stepped portion formed by TFTs. It isappropriate that the thickness is made 1 to 5 μm (more preferably 2 to 4μm).

[0127] Thereafter, a contact hole is formed in the second interlayerinsulating film 345 and the first passivation film 344 to reach thedrain wiring 343, and then the pixel electrode 346 is formed. In thepresent embodiment, an aluminum alloy film (an aluminum film containingtitanium of 1 wt %) having a thickness of 300 nm is formed as the pixelelectrode 346. Reference numeral 347 denotes an end portion of theadjacent pixel electrode.

[0128] Then, the alkaline compound 348 is formed, as shown in FIG. 6C.In the present embodiment, a lithium fluoride film is formed by a vapordeposition method so as to have a film thickness of 5 nm. Thereafter,the EL layer 349 having a thickness of 100 nm is formed by spin coating.

[0129] In the present embodiment, as the polymer type organic materialfor providing light of white color, the materials disclosed in JapaneseLaid-Open Patent Publication No. Hei 8-96959 or No. Hei 9-63770 can beused. For example, the material obtained by solving PVK (polyvinylcarbazole), Bu-PBD(2-(4′-tert-butylphenyl)-5-(4″-biphenyl)-1,3,4-oxydiazole), coumarin 6,DCM 1 (4-dicyanomethylene-2-methyl-6-p-dimethyl aminostilyl-4H-pyran),TPB (tetra phenyl butadiene), and Nile Red into 1,2-dichloromethane canbe used.

[0130] In the present embodiment, the EL layer 349 has a single layerstructure including only the above-mentioned light emitting layer.Alternatively, an electron injection layer, an electron transport layer,a hole transport layer, a hole injection layer, an electron blockinglayer, or a hole element layer can be further formed, if necessary.

[0131] Then, the anode 350 made of a transparent conductive film havinga thickness of 200 nm is formed to cover the EL layer 349. In thisembodiment, a film made of a compound of indium oxide and zinc oxide isformed by a vapor deposition and then patterned to obtain the anode.

[0132] Next, the metal film 351 made from low resistivity metal isformed on the anode 350. Further, ir is preferable to use the metalmaterial of the film thickness of metal film 351, which has lower filmresistivity than that of the anode 350.

[0133] The etching is performed after a deposition of the metal film351, because the metal film 351 is provided so as to conceal the gapbetween the pixel electrodes by seeing the direction of observation'seyes (a direction of a normal line of counter substrate). At this time,it is critical not to perform the etching simultaneously to the anode350. In this embodiment, the dry etching method is used as a mean ofetching and chloric gas is used for etching gas considering that theanode 350 is made of a compound of indium oxide and zinc oxide. In thisembodiment, a laminated structure which is deposition of titanium andaluminum by vapor deposition is formed, and the metal film 351 is formedby titanium having a thickness of 50 nm on the anode 350 and aluminumhaving a thickness of 250 nm on the titanium.

[0134] The electrolytic corrosion (also referred to electrical chemicalcorrosion) can be prevented by a structure that titanium is put betweenthe anode 350 and aluminum. Titanium nitride can be used as asubstitution for titanium which is used here. Titanium nitride has anadvantage of easy to contact electrically to the anode.

[0135] In this embodiment, the vapor deposition is used considering thata damage to the anode, but sputtering method can also be used.

[0136] The metal film 351 in the present invention is a laminatedstructure, but a single structure can be also applied to.

[0137] Finally, the second passivation film 351 made of a siliconnitride film is formed by a plasma CVD to have a thickness of 100 nm.This second passivation film 351 is intended to provide protection forthe EL layer 349 against water or the like, and also function to releaseheat generated in the EL layer 349. In order to further enhance the heatradiation effect, it is advantageous to form the second passivation filmby forming a silicon nitride film and a carbon film (preferably adiamond-like carbon film) into the lamination structure.

[0138] In this way, an active matrix EL display device having astructure as shown in FIG. 6C is completed. In the active matrix ELdisplay device of this embodiment, a TFT having an optimum structure isdisposed in not only the pixel portion but also the driver circuitportion, so that very high reliability is obtained and operationcharacteristics can also be improved.

[0139] First, a TFT having a structure to decrease hot carrier injectionso as not to drop the operation speed thereof as much as possible isused as an n-channel type TFT 205 of a CMOS circuit which constitutes adriver circuit. Note that the driver circuit here includes a shiftregister, a buffer, a level shifter, a sampling circuit (sample and holdcircuit) and the like. In the case where digital driver is made, asignal conversion circuit such as a D/A converter can also be included.

[0140] In the case of this embodiment, as shown in FIG. 6C, the activelayer of the n-channel TFT 205 includes a source region 355, a drainregion 356, an LDD region 357 and a channel forming region 358, and theLDD region 357 overlaps with the gate electrode 313 through the gateinsulating film 311.

[0141] Consideration not to drop the operation speed is the reason whythe LDD region is formed at only the drain region side. In thisn-channel type TFT 205, it is not necessary to pay attention to an offcurrent value very much, rather, it is better to give importance to anoperation speed. Thus, it is desirable that the LDD region 357 is madeto completely overlap with the gate electrode to decrease a resistancecomponent to a minimum. That is, it is preferable to remove theso-called offset region.

[0142] Furthermore, deterioration of the p-channel type TFT 206 in theCMOS circuit due to the injection of hot carriers is almost negligible,and thus, it is not necessary to provide any LDD region for thep-channel type TFT 206. It is of course possible to provide the LDDregion for the p-channel type TFT 206, similarly for the n-channel typeTFT 205, to exhibit countermeasure against the hot carriers.

[0143] Note that, among the driver circuits, the sampling circuit issomewhat unique compared to the other circuits, in that a large electriccurrent flows in both directions in the channel forming region. Namely,the roles of the source region and the drain region are interchanged. Inaddition, it is necessary to control the value of the off current to beas small as possible, and with that in mind, it is preferable to use aTFT having functions which are on an intermediate level between theswitching TFT and the current controlling TFT in the sampling circuit.

[0144] Accordingly, in the n-channel type TFT for forming the samplingcircuit, it is desirable to arrange the TFTs having the structure asshown in FIG. 10. As illustrated in FIG. 10, portions of the LDD regions901 a and 901 b overlap the gate electrode 903 through the gateinsulating film 902. The advantages obtainable by this structure havebeen already described with respect to the current controlling TFT 202.In the case where the TFT is used for the sampling circuit, the LDDregions are disposed to interpose the channel forming region 904therebetween.

[0145] In the actual process, after the structure shown in FIG. 6C iscompleted, the EL layer is sealed in the closed space by using thecounter substrate provided with the light shielding film, as previouslydescribed with reference to FIGS. 1 and 2. At this time, the reliability(lifetime) of the EL layer can be improved by setting an inertatmosphere within the closed space or disposing a moisture absorbingmaterial (e.g., barium oxide) in the closed space.

[0146] After the sealing process of the active matrix substrate and thecounter substrate is completed, a connector (flexible print circuit:FPC) is attached for connecting the terminals extended from the elementsor circuits formed on the substrate to external signal terminals,thereby completing a final product.

[0147] Here, the structure of the active matrix EL display device ofthis embodiment will be described with reference to a perspective viewof FIG. 7. The active matrix EL display device of this embodiment isconstituted by a pixel portion 602, a gate side driver circuit 603, anda source side driver circuit 604 formed on a glass substrate 601. Aswitching TFT 605 of a pixel portion is an n-channel type TFT, and isdisposed at an intersection point of a gate wiring line 606 connected tothe gate side driver circuit 603 and a source wiring line 607 connectedto the source side driver circuit 604. The drain of the switching TFT605 is connected to the gate of a current controlling TFT 608.

[0148] Furthermore, the source side of the current controlling TFT 608is connected to the power supply line 609. In the structure inaccordance with the present embodiment, an arbitrary voltage is appliedto the power supply line 609. The drain of the current controlling TFT608 is connected to the EL element 610.

[0149] The connection wiring lines 612 and 613 for transmitting signalsto the driver circuits and a connection wiring line 614 connected to thecurrent supply line 609 are provided in an FPC 611 as an externalinput/output terminal.

[0150] An example of circuit structure of the EL display device shown inFIG. 7 is shown in FIG. 8. The EL display device of this embodimentincludes a source side driver circuit 701. a gate side driver circuit(A) 707, a gate side driver circuit (B) 711, and a pixel portion 706.Note that in the present specification, the term driver circuit is ageneral term including the source side driver circuit and the gate sidedriver circuit.

[0151] The source side driver circuit 701 is provided with a shiftregister 702, a level shifter 703, a buffer 704, and a sampling circuit(sample and hold circuit) 705. The gate side driver circuit (A) 707 isprovided with a shift register 708, a level shifter 709, and a buffer710. The gate side driver circuit (B) 711 also has the same structure.

[0152] Here, the shift registers 702 and 708 have driving voltages of 5to 16 V (typically 10 V) respectively, and the structure indicated by205 in FIG. 6C is suitable for an n-channel type TFT used in a CMOScircuit forming the circuit.

[0153] Besides, for each of the level shifters 703 and 709 and thebuffers 704 and 710, similarly to the shift register, the CMOS circuitincluding the n-channel type TFT 205 of FIG. 6C is suitable. Note thatit is effective to make a gate wiring line a multi-gate structure suchas a double gate structure or a triple gate structure in improvingreliability of each circuit.

[0154] Besides, since the source region and the drain region areinverted and it is necessary to decrease an off current value, a CMOScircuit including the n-channel type TFT 208 of FIG. 10 is suitable forthe sampling circuit 705.

[0155] The pixel portion 706 is disposed with pixels having thestructure shown in FIG. 2.

[0156] The foregoing structure can be easily realized by manufacturingTFTs in accordance with the manufacturing steps shown in FIGS. 4A to 6C.In this embodiment, although only the structure of the pixel portion andthe driver circuit is shown, if the manufacturing steps of thisembodiment are used, it is possible to form a logical circuit other thanthe driver circuit, such as a signal dividing circuit, a D/A convertercircuit, an operational amplifier circuit, a γ-correction circuit, orthe like on the same substrate, and further, it is considered that amemory portion, a microprocessor, or the like can be formed.

[0157] Furthermore, the EL display device in accordance with the presentembodiment will be described with reference to FIGS. 11A and 11B. Thereference signs used in FIGS. 7 and 8 are referred if necessary.

[0158] A substrate 1000 (including a base film beneath TFTs) is anactive matrix substrate. On the substrate, a pixel portion 1001, asource side driver circuit 1002, and a gate side driver circuit 1003 areformed. Various wirings from the respective driver circuits are extendedthrough connection wirings 612 to 614 to reach an FPC 611 and beconnected to an external device.

[0159] At this time, a counter substrate 1004 is provided to surround atleast the pixel portion, and more preferably, the driver circuits andthe pixel portion. The counter substrate 1004 is adhered to the activematrix substrate 1000 by means of an adhesive (sealing agent) 1005 toform a closed space 1006. Thus, the EL element is completely sealed inthe closed space 1006 and shut out from the external air.

[0160] In the present embodiment, a photocurable epoxy resin is used asthe adhesive 1005. Alternatively, other adhesives such as an acrylatetype resin can also be used. A thermosetting resin can be also used ifacceptable in view of heat-resistance of the EL element. Note that thematerial is required to prevent oxygen and water from passingtherethrough as much as possible. The adhesive 1005 can be applied by acoating device such as a dispenser.

[0161] Furthermore, in the present embodiment, the closed space 1006between the counter substrate 1004 and the active matrix substrate 1000is filled with nitrogen gas. The black painted portion 1007 in FIG. 11Ais showed as an alloy film, practically, provided to fill the gapbetween the pixel electrodes on the anode 1008. In this embodiment, asan alloy film 1007, the laminated structured alloy film which iscomposed of vapor evaporated titanium and aluminum.

[0162] Furthermore, as shown in FIG. 11B, the pixel portion is providedwith a plurality of pixels each including an individually separated ELelement. All of these EL elements share an anode 1008 as a commonelectrode. The EL layer may be provided only in the pixel portion, butis not required to be disposed over the driver circuits. In order toselectively provide the EL layer, a vapor deposition method employing ashadow mask, a lift-off method, a dry etching method, or a laserscribing method can be used.

[0163] The anode 1008 is electrically connected to a connection wiring1009. The connection wiring 1009 is a power supply line to be used forsupplying a predetermined voltage to the anode 1008, and is connected tothe FPC 611 through a conductive paste material 1010. Although only theconnection wiring 1009 is described herein, the other connection wirings612 to 614 are also electrically connected to the FPC 611 in the similarmanner.

[0164] As described above, the structure as shown in FIG. 11 can displayan image on its pixel portion by connecting the FPC 611 to a terminal ofan external device. In the present specification, the EL display deviceis defined as a product in which an image display becomes possible whenan FPC is attached thereto, in other words, a product obtained byattaching an active matrix substrate to a counter substrate includingthe one provided with an FPC attached thereto.

[0165] [Embodiment 2]

[0166] Although the description has been made on the case of the topgate type TFT in the embodiment 1, the present invention is not limitedto the TFT structure, and may be applied to a bottom gate type TFT(typically, inverted stagger type TFT). Besides, the inverted staggertype TFT may be formed by any means.

[0167] Since the inverted stagger type TFT has such a structure that thenumber of steps can be easily made smaller than the top gate type TFT,it is very advantageous in reducing the manufacturing cost, which is theobject of the present invention. Incidentally, the structure of thisembodiment can be freely combined with any structure of the embodiment1.

[0168] [Embodiment 3]

[0169]FIG. 3B shows that the amount of the off current value in theswitching TFT in the pixel of the EL display device is reduced by usinga multi-gate structure for the switching TFT, and the need for a storagecapacitor is eliminated. However, it is also acceptable to make astructure of disposing a storage capacitor as is done conventionally. Inthis case, as shown in FIG. 12, a storage capacitor 1301 is formed inparallel to the gate of the current controlling TFT 202 with respect tothe drain of the switching TFT 201.

[0170] Note that the constitution of embodiment 3 can be freely combinedwith any constitution of embodiments 1 and 2. Namely, a storagecapacitor is merely formed within a pixel and it is not to limit the TFTstructure, materials of EL layer, etc.

[0171] [Embodiment 4]

[0172] Laser crystallization is used as the means of forming thecrystalline silicon film 302 in embodiment 1, and a case of using adifferent means of crystallization is explained in embodiment 4.

[0173] After forming an amorphous silicon film in embodiment 4,crystallization is performed using the technique described in JapanesePatent Application Laid-open No. Hei 7-130652. The technique describedin the above patent application is one of obtaining a crystallinesilicon film having good crystallinity by using an element such asnickel as a catalyst for promoting crystallization.

[0174] Further, after the crystallization process is completed, aprocess of removing the catalyst used in the crystallization may beperformed. In this case, the catalyst may be gettered using thetechnique described in Japanese Patent Application Laid-open No. Hei10-270363 or Japanese Patent Application Laid-open No. Hei 8-330602.

[0175] In addition, a TFT may be formed using the technique described inthe specification of Japanese Patent Application No. Hei 11-076967 bythe applicant of the present invention.

[0176] The manufacturing processes shown in embodiment 1 are oneembodiment of the present invention, and provided that the structure ofFIG. 2 or of FIG. 6C of embodiment 1 can be realized, then othermanufacturing process may also be used without any problems, as above.

[0177] Note that it is possible to freely combine the constitution ofembodiment 4 with the constitution of any of embodiments 1 to 3.

[0178] [Embodiment 5]

[0179] The first embodiment shows the structure in which the metal film109 is provided on the anode 108 in the EL device so as to conceal thegaps 111 between the adjacent pixel electrodes. In the presentembodiment, as shown in FIG. 15, a metal thin film 114 is formed on theanode 108 so as to be interposed between the anode 108 and the metalfilm 109.

[0180] A film thickness of the metal thin film 114 is set so as not tolose transparency, specifically in the range from 10 to 50 nm(preferably in the range from 20 to 30 nm). On the metal thin film 114,the metal film 109 is formed in a manner similar to Embodiment 1.

[0181] By providing the layered structure including the metal thin film114 and the metal film 109 on the anode 108 in the EL device, an averagefilm resistance of the anode can be decreased.

[0182] The structure in the present embodiment can be freely combinedwith any structure described in the previous embodiments.

[0183] [Embodiment 6]

[0184] The first embodiment shows the structure in which the metal film109 is provided on the anode 108 in the EL device so as to conceal thegaps III between the adjacent pixel electrodes. In the presentembodiment, as shown in FIG. 15, a metal thin film 114 made of chromiumis formed on the anode 108 so as to be interposed between the anode 108and the metal film 109 which will now be explained.

[0185] A film thickness of the metal thin film 114 is set so as not tolose transparency, specifically at about 50 nm (preferably at about 30nm). On the metal thin film 114, the metal film 109 is formed in themanner similar to Embodiment 1.

[0186] By providing the layered structure including the metal thin film114 and the metal film 109 on the anode 108 in the EL device, an averagefilm resistance of the anode 108 can be decreased.

[0187] In the case where the anode 108 is made of a compound of indiumoxide and tin oxide and the metal film 109 is made of aluminum in thepresent embodiment, the metal thin film 114 made of chromium canfunction to prevent electrical corrosion from occurring between theanode 108 and the metal film 109.

[0188] Furthermore, the metal thin film 114 made of chromium and themetal film 109 made of aluminum, as used in the present embodiment, canexhibit a sufficiently large selection ratio against a chlorine typeetching gas. Thus, they are effective in the case where only the metalfilm 109 is to be selectively dry etched.

[0189] The structure in the present embodiment can be freely combinedwith any structure described in the previous embodiments.

[0190] [Embodiment 7]

[0191] In driving the EL display device of the present invention, analogdriving can be performed using an analog signal as an image signal, anddigital driving can be performed using a digital signal.

[0192] When analog driving is performed, the analog signal is sent to asource wiring of a switching TFT, and the analog signal, which containsgray scale information, becomes the gate voltage of a currentcontrolling TFT. The current flowing in an EL element is then controlledby the current controlling TFT, emitting intensity of the EL element iscontrolled, and gray scale display is performed.

[0193] On the other hand, in the case of digital driving, gray scaledisplay referred to as “time-division driving” is performed unlike thegray scale display on an analog basis. Specifically, the emitting timeis adjusted to provide visual appearance that seems like changes incolor gradation. The EL element has an extremely fast response speed incomparison to a liquid crystal element, and therefore it is possible tohave high speed driving. Therefore, the EL element is one, which issuitable for time division driving, in which one frame is partitionedinto a plural number of sub-frames and then gray scale display isperformed.

[0194] The present invention is a technique related to the elementstructure, and therefore any method of driving it may thus be used.

[0195] Note that the structure of this embodiment can be freely combinedwith any structure of the embodiments 1 to 6.

[0196] [Embodiment 8]

[0197] The EL display device uses light emitted from itself to displayan image, and thus, does not require any back light. A reflection typeliquid crystal display device requires a back light in a dark placewhere sufficient light is not available, although it has a feature inthat an image can be displayed with outdoor light. On the other hand,the EL display device is not suffered from such a disadvantage in a darkplace, since it is of the self-emission type.

[0198] However, when an electronic device including the EL displaydevice as its display portion is actually used outdoors, it may be ofcourse used both in a light place and in a dark place. In such asituation, an image can be sufficiently recognized in a dark place evenwhen the luminance is not so high, while an image may not be recognizedin a light place if the luminance is not sufficiently high.

[0199] An amount of light emitted from the EL layer varies depending onan amount of current to flow. Thus, a larger amount of current to flowrequires the higher luminance, resulting in an increased powerconsumption. However, when the luminance of emitted light is set at sucha high level, too brighter image than necessary with too large powerconsumption will be displayed in a dark place.

[0200] In order to overcome the above-mentioned disadvantage, the ELdisplay device in accordance with the present invention preferably has afunction to detect the lightness in the surrounding atmosphere by meansof a sensor, and adjust the luminance of the light emitted from the ELlayer in accordance with the sensed lightness. More specifically, theluminance of the emitted light is set at a high level in a light place,while at a low level in a dark place, so that an increase in powerconsumption is avoided. Thus, the EL display device in accordance withthe present invention can realize reduction in power consumption.

[0201] As a sensor to be used for detecting lightness in the surroundingatmosphere, a CMOS sensor, a CCD or the like can be used. A CMOS sensorcan be formed with any known technique on the identical substrate withdriver circuits and a pixel portion of the EL display device. Asemiconductor chip on which a CCD is formed can be attached onto the ELdisplay device. Alternatively, a CCD or a CMOS sensor may be provided asa portion of an electronic device including the EL display device as itsdisplay portion.

[0202] A circuit for adjusting a current to flow into the EL layer basedon a signal obtained by the sensor for detecting the lightness in thesurrounding atmosphere is provided. Thus, the luminance of the lightemitted from the EL layer can be adjusted in accordance with thelightness in the surrounding atmosphere.

[0203] The structure in the present embodiment is applicable incombination with any structure in Embodiments 1 to 7.

[0204] [Embodiment 9]

[0205] The EL display device fabricated in accordance with the presentinvention is of the self-emission type, and thus exhibits more excellentrecognizability of the displayed image in a light place as compared tothe liquid crystal display device. Furthermore, the EL display devicehas a wider viewing angle. Accordingly, the EL display device can beapplied to a display portion in various electronic devices. For example,in order to view a TV program or the like on a large-sized screen, theEL display device in accordance with the present invention can be usedas a display portion of an EL display (i.e., a display in which an ELdisplay device is installed into a frame) having a diagonal size of 30inches or larger (typically 40 inches or larger).

[0206] The EL display includes all kinds of displays to be used fordisplaying information, such as a display for a personal computer, adisplay for receiving a TV broadcasting program, a display foradvertisement display. Moreover, the EL display device in accordancewith the present invention can be used as a display portion of othervarious electric devices.

[0207] Such electronic devices include a video camera, a digital camera,a goggle-type display (head mount display), a car navigation system, acar audio equipment, note-size personal computer, a game machine, aportable information terminal (a mobile computer, a portable telephone,a portable game machine, an electronic book, or the like), an imagereproduction apparatus including a recording medium (more specifically,an apparatus which can reproduce a recording medium such as a compactdisc (CD), a laser disc (LD), a digital video disc (DVD), and includes adisplay for displaying the reproduced image), or the like. Inparticular, in the case of the portable information terminal, use of theEL display device is preferable, since the portable information terminalthat is likely to be viewed from a tilted direction is often required tohave a wide viewing angle. FIG. 13 shows various specific examples ofsuch electronic devices.

[0208]FIG. 13A illustrates an EL display which includes a frame 2001, asupport table 2002, a display portion 2003, or the like. The presentinvention is applicable to the display portion 2003. The EL display isof the self-emission type and therefore requires no back light. Thus,the display portion thereof can have a thickness thinner than that ofthe liquid crystal display device.

[0209]FIG. 13B illustrates a video camera which includes a main body2101, a display portion 2102, an audio input portion 2103, operationswitches 2104, a battery 2105, an image receiving portion 2106, or thelike. The EL display device in accordance with the present invention canbe used as the display portion 2102.

[0210]FIG. 13C illustrates a portion (the right-half piece) of an ELdisplay of head mount type, which includes a main body 2201, signalcables 2202, a head mount band 2203, a projection portion 2204, anoptical system 2205, a display portion 2206, or the like. The presentinvention is applicable to the display portion 2206.

[0211]FIG. 13D illustrates an image reproduction apparatus including arecording medium (more specifically, a DVD reproduction apparatus),which includes a main body 2301, a recording medium (a CD, an LD, a DVDor the like) 2302, operation switches 2303, a display portion (a) 2304,another display portion (b) 2305, or the like. The display portion (a)is used mainly for displaying image information, while the displayportion (b) is used mainly for displaying character information. The ELdisplay device in accordance with the present invention can be used asthese display portions (a) and (b). The image reproduction apparatusincluding a recording medium further includes a CD reproductionapparatus, a game machine or the like.

[0212]FIG. 13E illustrates a portable (mobile) computer which includes amain body 2401, a camera portion 2402, an image receiving portion 2403,operation switches 2404, a display portion 2405, or the like. The ELdisplay device in accordance with the present invention can be used asthe display portion 2405.

[0213]FIG. 13F illustrates a personal computer which includes a mainbody 2501, a frame 2502, a display portion 2503, a key board 2504, orthe like. The EL display device in accordance with the present inventioncan be used as the display portion 2503.

[0214] When the brighter luminance of light emitted from the EL materialbecomes available in the future, the EL display device in accordancewith the present invention will be applicable to a front-type orrear-type projector in which light including output image information isenlarged by means of lenses or the like to be projected.

[0215] The aforementioned electronic devices are more likely to be usedfor display information distributed through a telecommunication pathsuch as Internet, a CATV (cable television system), and in particularlikely to display moving picture information. The EL display device issuitable for displaying moving pictures since the EL material canexhibit high response speed. However, if the contour between the pixelsbecomes unclear, the moving pictures as a whole cannot be clearlydisplayed. Since the EL display device in accordance with the presentinvention can make the contour between the pixels clear, it issignificantly advantageous to apply the EL display device of the presentinvention to a display portion of the electronic devices.

[0216] A portion of the EL display device that is emitting lightconsumes power, so it is desirable to display information in such amanner that the light emitting portion therein becomes as small aspossible. Accordingly, when the EL display device is applied to adisplay portion which mainly displays character information. e.g. adisplay portion of a portable information terminal, and more particular,a portable telephone or a car audio equipment, it is desirable to drivethe EL display device so that the character information is formed by alight-emitting portion while a non-emission portion corresponds to thebackground.

[0217] With now reference to FIG. 14A, a portable telephone isillustrated, which includes a main body 2601, an audio output portion2602, an audio input portion 2603, a display portion 2604, operationswitches 2605, and an antenna 2606. The EL display device in accordancewith the present invention can be used as the display portion 2604. Thedisplay portion 2604 can reduce power consumption of the portabletelephone by displaying white-colored characters on a black-coloredbackground.

[0218]FIG. 14B illustrates a car audio equipment which includes a mainbody 2701, a display portion 2702, and operation switches 2703 and 2704.The EL display device in accordance with the present invention can beused as the display portion 2702. Although the car audio equipment ofthe mount type is shown in the present embodiment, the present inventionis also applicable to a car audio of the set type. Note that the displayportion 2704 can reduce power consumption by displaying white-coloredcharacters on a black-colored background.

[0219] As set forth above, the present invention can be appliedvariously to a wide range of electronic devices in all fields. Theelectronic device in the present embodiment can be obtained by utilizingan EL display device having the configuration in which the structures inEmbodiments 1 through 8 are freely combined.

[0220] [Embodiment 10]

[0221] In the present invention, among the light emitted from the ELlayer, portions thereof emitted toward the cathode side are reflectedfrom the cathode and then emitted through the anode side.

[0222] In this case, with respect to the regions where the EL layer isemitting light, a light having a wavelength determined based on theconstituent material of the light emitting layer can be visible.However, in the other regions that do not emit light, a rear surfaceside of the cathode (i.e., the surface closer to the light emittinglayer) can be seen through the anode and the EL layer. Thus, adisadvantage arises in which the rear surface of the cathode functionsas a mirror to reflect a viewer's face. In the present embodiment, anexample for overcoming such a disadvantage will be described.

[0223] As the simplest method for overcoming the disadvantage, acircularly polarizing film can be adhered to the EL display device.However, this undesirably results in an increased cost since thecircularly polarizing film is expensive. As an alternative method, it ispossible to provide raised portions on the reflecting surface (i.e., onthe surface closer to the light emitting layer) of the cathode so as toscatter the light reflected from the reflecting surface of the cathode.

[0224] More specifically, the visible light (external light) incidentfrom the anode side is allowed to be randomly reflected from thereflecting surface of the cathode, thereby preventing the reflectingsurface of the cathode from being visible to a viewer.

[0225] The raised portions to be provided on the reflecting surface ofthe cathode may be formed by providing concave recesses or convexprojections. Alternatively, a corrugated surface may be provided inwhich concave and convex portions are repeatedly formed. The raisedportions as mentioned above may be formed by a photo-lithographicformation technique, a holographic formation technique (for example, theconcave and convex reflection structure described in Sharp TechnicalReport, Vol.74, pp. 16-19, Issue of August, 1999) or the like.Alternatively, the raised portions may be formed by a surface treatmentmethod such as a plasma process, an etching process, or the like.Furthermore, the raised portions may be naturally formed on the surfaceof the cathode depending on the deposition conditions of the cathode (orthe deposition condition of the electrode underlying the cathode).

[0226] In other words, although the raised portions may be providedeither regularly or irregularly, they have to be provided so as to allowrandom reflection to occur in an averaged manner within the in-plane ofthe respective pixels. Alternatively, the raised portions may be formedon the other thin film contacting the cathode. In particular, thetechniques described in Japanese Patent Application Laid-Open Nos. Hei.9-69642 and 10-144927 can be employed as the measure for forming theraised portions on an aluminum film. More specifically, an aluminum filmmay be formed in accordance with the techniques described in theabove-mentioned publications and a cathode is then deposited on the thusformed aluminum film, thereby resulting in the cathode having the raisedportions provided thereon.

[0227] By employing the technique as mentioned above, a viewer's face isprevented from being reflected from and seen on the rear surface of thecathode. The structure in the present embodiment can be freely combinedwith any structure described in the previous embodiments.

[0228] Thus, as set forth above, by implementing the present invention,an average film resistance of the anode can be reduced by the metal filmprovided on the anode. Furthermore, the above-mentioned metal film is alight-shielding film which is disposed so as to conceal the gaps betweenthe pixels, thereby resulting in clearer contours between the pixelelectrodes in the pixel section. Thus, an EL display device capable ofdisplaying an image with high definition can be obtained. Moreover, byutilizing the EL display device in accordance with the present inventionas a display section, electrical equipment with the high reliability andhigh visibility can be provided.

What is claimed is:
 1. An EL display device comprising: an active-matrixsubstrate over which pixels are arranged, each of said pixels having apixel electrode electrically connected to a thin-film transistor; and anEL element comprising said pixel electrode as a cathode, an EL layer,and an anode, wherein a metal film is provided on said anode so as toconceal edges of said pixels and gaps between said pixels.
 2. An ELdisplay device according to claim 1, wherein a film resistance of saidmetal film is lower than a film resistance of said anode.
 3. An ELdisplay device according to claim 1, wherein said metal film functionsas a light-shielding film.
 4. An EL display device according to claim 1,wherein said metal film has a layered structure.
 5. An EL display deviceaccording to claim 1, wherein raised portions are provided on a surfaceof said cathode of said EL element.
 6. An EL display device according toclaim 1, wherein an element of said metal film is one selected from thegroup consisting of Ti, Al, Ta, W, Cr, Cu, and Ag.
 7. An EL displaydevice according to claim 1, wherein said anode comprises indium tinoxide.
 8. An EL display device according to claim 1, wherein saidcathode comprises aluminum.
 9. An EL display device according to claim1, wherein said EL display device is one selected from the groupconsisting of a video camera, a head-mount display, a personal computer,a car navigation system, a mobile telephone, and a car audio equipment.10. An EL display device comprising: an active-matrix substrate overwhich pixels are arranged, each of said pixels having a pixel electrodeelectrically connected to a thin-film transistor; and an EL elementcomprising said pixel electrode as a cathode, an EL layer, and an anode,wherein a metal film is provided between said anode and a countersubstrate so as to conceal edges of said pixels and gaps between saidpixels.
 11. An EL display device according to claim 10, wherein a filmresistance of said metal film is lower than a film resistance of saidanode.
 12. An EL display device according to claim 10, wherein saidmetal film functions as a light-shielding film.
 13. An EL display deviceaccording to claim 10, wherein said metal film has a layered structure.14. An EL display device according to claim 10, wherein raised portionsare provided on a surface of said cathode of said EL element.
 15. An ELdisplay device according to claim 10, wherein an element of said metalfilm is one selected from the group consisting of Ti, Al, Ta, W, Cr, Cu,and Ag.
 16. An EL display device according to claim 10, wherein saidanode comprises indium tin oxide.
 17. An EL display device according toclaim 10, wherein said cathode comprises aluminum.
 18. An EL displaydevice according to claim 10, wherein said EL display device is oneselected from the group consisting of a video camera, a head-mountdisplay, a personal computer, a car navigation system, a mobiletelephone, and a car audio equipment.
 19. An EL display devicecomprising: an active-matrix substrate over which pixels are arranged,each of said pixels having a pixel electrode electrically connected to athin-film transistor; and an EL element comprising said pixel electrodeas a cathode, an EL layer, and an anode, wherein a metal film isprovided on a portion of said anode so as to conceal gaps between saidpixel electrodes.
 20. An EL display device according to claim 19,wherein a film resistance of said metal film is lower than a filmresistance of said anode.
 21. An EL display device according to claim19, wherein said metal film functions as a light-shielding film.
 22. AnEL display device according to claim 19, wherein said metal film has alayered structure.
 23. An EL display device according to claim 19,wherein raised portions are provided on a surface of said cathode ofsaid EL element.
 24. An EL display device according to claim 19, whereinan element of said metal film is one selected from the group consistingof Ti, Al, Ta, W, Cr, Cu, and Ag.
 25. An EL display device according toclaim 19, wherein said anode comprises indium tin oxide.
 26. An ELdisplay device according to claim 19, wherein said cathode comprisesaluminum.
 27. An EL display device according to claim 19, wherein saidEL display device is one selected from the group consisting of a videocamera, a head-mount display, a personal computer, a car navigationsystem, a mobile telephone, and a car audio equipment.
 28. An EL displaydevice comprising: an active-matrix substrate over which pixels arearranged, each of said pixels having a pixel electrode electricallyconnected to a thin-film transistor; and an EL element comprising saidpixel electrode as a cathode, an EL layer, and an anode, wherein a metalfilm is provided between a portion of said anode and a counter substrateso as to conceal gaps between said pixel electrodes.
 29. An EL displaydevice according to claim 28, wherein a film resistance of said metalfilm is lower than a film resistance of said anode.
 30. An EL displaydevice according to claim 28, wherein said metal film functions as alight-shielding film.
 31. An EL display device according to claim 28,wherein said metal film has a layered structure.
 32. An EL displaydevice according to claim 28, wherein raised portions are provided on asurface of said cathode of said EL element.
 33. An EL display deviceaccording to claim 28, wherein an element of said metal film is oneselected from the group consisting of Ti, Al, Ta, W, Cr, Cu, and Ag. 34.An EL display device according to claim 28, wherein said anode comprisesindium tin oxide.
 35. An EL display device according to claim 28,wherein said cathode comprises aluminum.
 36. An EL display deviceaccording to claim 28, wherein said EL display device is one selectedfrom the group consisting of a video camera, a head-mount display, apersonal computer, a car navigation system, a mobile telephone, and acar audio equipment.